Just made a mobile to another mobile from Australia to UK and was amazed by how clear and non laggy it was. How does the signal get sent back and forth from one side of the world to the other? Satellite or cable? Radio or fibre optic?
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Calls will go via fibre-optic cables.
For several decades now, they’ve been transmitted all-digitally, so there won’t be any quality degradation.
Earth radius is 6378km. Halfway around the earth’s surface is pi*r, so 20,000 km
Speed of light in air is 3×10^(8) m/s, or 300,000 km/s, but in fibre optic is about 2/3 the speed of light in air/vacuum, so around 200,000 km/s.
Therefore it’ll take the light one tenth of a second to go halfway around the world.
The perceived delay is the round-trip time, so two-tenths of a second (1/5th second). This is the fastest it could possibly be. In reality the route will not be the shortest possible, and there might be a few other routing delays along the way.
This delay is fairly imperceptible, and probably shorter than coding/decoding delays that you get in any mobile call, even between two people standing next to each other.
Calls will go via fibre-optic cables.
For several decades now, they’ve been transmitted all-digitally, so there won’t be any quality degradation.
Earth radius is 6378km. Halfway around the earth’s surface is pi*r, so 20,000 km
Speed of light in air is 3×10^(8) m/s, or 300,000 km/s, but in fibre optic is about 2/3 the speed of light in air/vacuum, so around 200,000 km/s.
Therefore it’ll take the light one tenth of a second to go halfway around the world.
The perceived delay is the round-trip time, so two-tenths of a second (1/5th second). This is the fastest it could possibly be. In reality the route will not be the shortest possible, and there might be a few other routing delays along the way.
This delay is fairly imperceptible, and probably shorter than coding/decoding delays that you get in any mobile call, even between two people standing next to each other.
I’ll add, even though it has already been well answered! You might want to check out this link: [https://www.submarinecablemap.com/](https://www.submarinecablemap.com/) These cables were first introduced about 100 years ago for telegrams between North America and Europe, still the best way to get messages across oceans.
Shows all of the cables underneath the oceans, the math is broken down by u/Prestigious_Carpet29. SAT Communication is also possible, again some delay occurs depending on signal travel time at the speed of light to the satellite, to the user on the other end, back up to the satellite and down to you with the response but way too fast for us to notice.
I’ll add, even though it has already been well answered! You might want to check out this link: [https://www.submarinecablemap.com/](https://www.submarinecablemap.com/) These cables were first introduced about 100 years ago for telegrams between North America and Europe, still the best way to get messages across oceans.
Shows all of the cables underneath the oceans, the math is broken down by u/Prestigious_Carpet29. SAT Communication is also possible, again some delay occurs depending on signal travel time at the speed of light to the satellite, to the user on the other end, back up to the satellite and down to you with the response but way too fast for us to notice.
Generally not via satellites, unless you happen to be using a satellite phone to make a call from a remote location because nothing else works – in which case you’d know about it.
Satellites are too expensive, and geostationary satellites, which are the only ones you can aim a satellite dish at without having to constantly move it, are much too far away. It talks about a quarter second for a signal to get up to a geostationary satellite and back to earth. So for a phone call for a signal to get from your voice via a satellite to your friend, and then for you to hear their response (which might be them stopping talking) via the same satellite it would add about a half second delay.
Generally not via satellites, unless you happen to be using a satellite phone to make a call from a remote location because nothing else works – in which case you’d know about it.
Satellites are too expensive, and geostationary satellites, which are the only ones you can aim a satellite dish at without having to constantly move it, are much too far away. It talks about a quarter second for a signal to get up to a geostationary satellite and back to earth. So for a phone call for a signal to get from your voice via a satellite to your friend, and then for you to hear their response (which might be them stopping talking) via the same satellite it would add about a half second delay.
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